Photometer.



H. G. AYLSWORTH.

PHOTOMETER.

APPLICATION mm AUG. 1. 1916.

Patented Jan. 7, 1919.

/NI 1. m 1010, HUWHEU 5. F'YL 5 W05 TH UNITED STATES PATENT OFFICE.

HOWARD G. AYLSWORTH.

OF SAN FRANCISCO, CALIFORNIA, ASSIG NOR OF ONE-THIRD T GEORGE A. DOLANAND ONE-THIRD TO WILLIAM WOLF, BOTH OF SAN FRANCISCO,

CALIFORNIA.

Specification of Letters Patent.

Patented Jan. 7, 1919.

Application filed August 1. 1916. Serial No. 112,525.

lie it known that l. llowauo (l. AYLswou'ru. a citizen of the UnitedStates, residing at San Francisco. in the county of San l ranoisco.State of (alit'oi-iiia, have invented a new and useful lhotonwter, ofwhich the following is a specification in such full and clear terms aswill enable those skilled in the art to construct and use. the same.

This invention relates to a photometer adapted to be applied to theshutter and diaphragm of a photographic lens to en able the user to:wcurately determine the time required foran exposure with any givenstop or the stop to use for any given time, the device being applied tothe tinder used for positioning the camera and having means connectedtherewith for determining the stop to use as well as the time ofexposure.

It. will be uiulerstood by those skilled in the art that in takingpictures with a plate of a given speed there are two variable factors.one, the time of exposure. and the other the size sto J used. so thatany means tor the tel-mining iJUlll of these factors must take accountof both of them.

In the present invention the illumination of the screen in the tinder ismade use of to determine the time and stop to use in making theexposure.

An emluuliment oi' the invention is shown in the drawing in which thesame reference numeral is applied to the same portion throughout. but. Iam aware that there may be many niodifications thereof.

Figure 1 is a. front elevation of a. lens tube having a common form ofiris diaphragm and iris shutter, and 1 Fig. 2 is a side elevation of thelens tube and tinder shown in Fig. 1.

The numeral 1 indicates the casing within which the operating mechanismfor the shutter leaves 2 and iris diaphragm 3 are. mounted, said shutterand diaphragm being of a. construction well known in the art. The lens iis applied to the front of the shutter casing and the tube 5 to the backthereof to connect the lens with the body of the camera.

The iris diaphragm is operated in a well known manner by means ol alever having a. pointer 6. while the shutter is set; as to time byshifting a lever having a pointer 7. the shutter being set off bypushing on a pin 8. all of the foregoing construction being well knownin the art and forming no part of the present invention.

lonnected with the casing operating mechanism for the shutter anddiaphragm is a secondary casing 9 which carries a finder box 10 having aI'Qflc' tor l1, lens 12 and ground glass 13. upon which the image madeby the finder lens is observed. In front of the finder lens there aretwo slidable plates 14, 15. said plates being cut at an angle withrespect to their slots 1G. 17 along which they slide. pins. [8, 19. 20and 21 determining: their path of travel.

The slidable plate 14 is pivotallv connected \vith'a link 22. which linkis in turn connected to the arm carrying the pointer (I. while the plate15 has a link 23 pivotallv connected therewith and pivotallv connectedwith the arm carrying the pointer 7.

Secured on the outside of the shutter casing are two plates 24. 25 whichplates are graduated in a manner well known to photographers to indicatethe size of the stop intended to be used. the pointers being movableacross said graduations to indicate the point at which the diaphragm andshutter respectively will operate in the way intended.

The operation of the device is as follows: In the first place it' is tobe observed that the brighter the ligiht the shorter the eX- posure canbe and the smaller the aperture can be. while the duller the light theslower will be the exposure and the larger must be the aperture. or. ita given aperture is desired or a given time dcsi red. as for example.when a person desires to take a snap shot it is known in advance that anexposure must be made in 1/25 of a second or less to prevent the picturefrom being blurred, the stop must then be changed to give the necessarylight.

lnthe present instance. the finder will be examined until a desiredillumination of its screen 13 is bad. which illumination will bedetermined by the holder of the apparatus and this illun'iination isobtained by increasing or diminishing the quantity of light that. isallowed to pass through the lens: 12hr raising or lowering either of theplates H or 15. \Vhcn the desired ilhunination of the screen 13 is hadthe exposure will be made in accordance with the indications of thepointers 6 and 7. t

It is to be observed that with properly earryi ng the shaped lenses forthe linder the style of Open ing through which they receive light fromthe ohjeetss lo lH' photographed matters lil tle, the only dill'ereneeliving that an llll lens is covered or nnvorered more or i055 light willhe delivered to the screen upon whivh the image is seen.

Having thus described my invention wlial I claim as ne and desire tosecure by Let tore Patent of the United States, is as follows, expressreservation being made of permia ihle I'HOLllfiCHLlUHSI l. A photonieler comprising a view finder. having a lens an opaque slide movableavrosa the tinder lens means to more the slide to giinlually ohsiiure oruni-over the finder lens a ianiera Inning a lens, a sl'nll'ler l'oi llmcamera lens. meam lo regulate the timing of the shutter, and a linkvonnegting the \lide and the said slnitier regulating apparatus wherehythe tinder lena will he lllUl'u obscured an the shutter time is deereawdand lt'551JlHClULLl as the shuller time is increased.

A photo meter eoniprising a view finder ha ring a lens, an opaque glidemovable across the lens of the finder, means to more the sliClQ togradually obscure or uncover the finder lens, a camera having a lens, adiaphragm for the camera lens. means to inrrease or diminish the openingin the camera diaphragm. and a link i -onneetion between lllt' diaphragmoperating lever and the opaque slide wherehy the tinder lens will hemore ohai'ured as the opening in the diaphragm is diminished and lessobscured as the opening in the diaphragm is increased.

3. A photo meter romprising a view finder having a lens, a pair ofopaque slides mew Hllll aprons the lindeilens to obscure or un rover it.a camera having a lens, a shutter for the camera lens, means to regulatethe timing of the shutter, a link between the .dialter timinglneehanisin and one of the linder alidem \\l1l71'9l) the linder lenswill he more Uli-f-llilll'll'l 11 the shutter time is de weaned and lessohsvui'ed as the shutter time, is inrreaswl, a diaphragm for the rameraInns having an opening means whereby the opening in the diaphragm may beint-reused or diminished in size, and a connection hi tween thediaphragm adjusting meehanism and ilh' of the lide for the tinderwherein an the diaphragm opening is increased the finder len, will hemore uncovered and Vice versa.

In testin'iony whereof I have hereunto set my hand this 27th day ofJuly, A. D. 1916.

HOlVARD G. A YLSWORTH.

